Shielding for high frequency switches



- SHIELDING FOR HIGH FREQUENCY SWITCHES Filed Oct. 2, 1941 Fig.1.

Inventor Harry F. Mager,

- His Attqrneg.

y the rotor.

Patented Nov 9, 1943 UNITED STATES PATENT OFFICE s'nmmnvo ron man mnoomvcr General New York Harry F.-Mayer, Schenectady, N. Y., assignor to Electric Company, a corporation of Application October z, 1941, Serial No. 413,312

- 6 Claims. (c1. zoo-c) My invention relates to switches for controlling high frequency circuits in radio apparatus and the like, particularly to gang switches in such apparatus for selecting frequency bands, and its general object is to provide switches of this character incorporating shielding'means which insure more emcient and stable operation of theapparatus. I 4

In multi-band radio apparatus the 7 gang switches commonly employed'for the purpose of band changing may comprise for each stage a movable supporting member'or rotor member of insulating material having mounted thereon a contact member or members engaging in suc-' cession fixed contacts connected to lnterstageelements or windings corresponding to the several frequency bands to be selected, and a contact member arranged to. ground the fixed contacts corresponding to the frequency bands other than the band selected, at any given band position of These switch assemblies or switch wafers for the several stages of the apparatus are spaced along a common operating shaft which traverses the insulating movable supporting or rotor members. 4

In multi-band high frequency radio apparatus it is essential to avoid or to reduce interstage coupling tending to cause undesirable oscillation and radiation, for example the coupling which may be caused by the relatively close proximity of the above mentioned selective switch'assemblies or wafers to each other, For the purpose of reducing the latter undesirable coupling it is easily possibleto shield the assemblies or wafers from each other practically perfectly. However, there still remains as a coupling means the operating shaft which, because of the severe torsional strains imposed thereon in operation of the numerous closely fitted sliding contacts of the switchassemblies or wafers, is commonly, of necessity'a single metal piece.

voltages originating in a loacl oscillator may be transmitted along the shaft to the antenna circult. causing objectionable radiation therefrom.

. In all cases with switch assemblies of the type described, the undesired interfering voltages are transmitted to'the switch-operating metal shaft largely from the ungrounded rotatable contact members or plates, and the fixed contacts connected therewith, upon which oscillations are impressed and which are mounted respectively on the rotor and ma fixed support, relatively very close to the shaft. v

In accordance with my present invention, I

have overcome to a marked extent the hcreinby a grounded shield plate mounted on the movable insulating support or rotor of one or more .-of the switch assemblies and between the latter particularity in the appended claims.

' tion and method of operation together with furcontact member or members and the metal shaft. v In a modification of my invention the shielding means is constituted by a grounded tubular shield member surrounding a portion of the metal shaftther objects and advantages thereof may best be voltages originate. In a series of radio frequency amplifiers, the oscillations may be of sulllcient magnitude to cause instability of a stage or' even to cause the stage to go into oscillation, and in an apparatus of the superheterodyne ty e oscillating 65 (not shown), and a gang switch arrangement for understood by reference to the following description taken in connectionjwith the accompanying drawing wherein Fig. 1 is a partially diagrammatic representation of a multi-band radio apparatus comprising an embodiment of the switch shielding system in accordance with my invention; Figs. 2, 3 and 4 respectively a front elevation, sectional view on line A-A, and a rear elevation of a usual switch assembly or switch wafer in which a shielding means in accordance with the invention has been embodied; and Figs. 5 and 6 are respectively a rear elevational view and a partially sectional view on line 3-3 of a switch assembly embodying a modification of the invention.

In Fig. 1 a transformer-coupled multi-band radio apparatus is shownhaving a usual antenna stage I,' tworadio frequency amplifierstages 2 and 3, a converterstage 4 the output of which selecting frequency bands which comprises switch assemblies or switch wafers 5 to 8 (illustrated diagrammatically) and an actuating metal shaft 3.

In switch assembly 8, for example, which is typical and the purpose of which in the system shown in Fig. 1 is to control an anode circuit and a grid circuit in. the local oscillator circuit associated with the converter stage 4, shaft 9 traverses an insulating rotor member In which supports on one side two contact members designated by the lines II and I2 and represented as slidably connected through fixed contacts I3 and I4 to sources of potential which in the present instance are constitutedby oscillator elements of the converter 4. The contact members ll and 12 are adapted to be connected, for the purpose of selecting frequency bands, through portions i5 and I5 of members II and I2, and thence through fixed contacts l1 to 20 and 2| to 24, to the high potential terminals of the primary and secondary windings of the coupling transformers, two of which, 25 and 26, are shown in Fig. 1, associated with the local oscillator circuit of converter stage 4.

The rotor member i supports on its other side a grounding member, designated by the line 21, adapted to connect to ground through a fixed contact 23 all of the high potential ends of the above mentioned local oscillator transformer windings except those of the transformer illus-v trated as 25 in Fig. 1, corresponding to the selected frequency band.

The other gang switch assemblies or switch wafersspaced along the operating shaft aresimilar to switch 8, the switches 5, and 1 being operatively associated respectively with banks of transformers adapted in the selecting of frequency bands to couple antenna stage I and the first amplifier 2, the first and second amplifiers 2 and'3, and the second amplifier 3 and the converter 4.

In accordance with my present invention, in order to reduce in amount any undesired coupling which is established between the antenna stage,

the radio frequency amplifier stages, and the converter stage through the metal operating shaft 8, a. grounded shielding means is provided be-,

tween the shaft and ungrounded elements of one or more of the switch assemblies 5 to 3, this shielding means being particularly desirable between the shaft and the rotatable ungrounded contact members, such as represented, for example, by II and I2 of switch 3. The latter contact members are located close tothe shaft and tend strongly to transmit undesired oscillations thereto.

. As shown semi-diagrammatically in connection with the switches 5 to 3 the shielding means may preferably take the form of a conductive member or plate 23 mounted on the same side of rotor II as the rotatable contact members H and I2, and extending closely adjacent to these contact members and to the shaft. The grounding of the the rotor are mounted two contact members or plates 32 and 33 of arcuate shape and on the other side is mounted a single grounding, member or plate 34 of circular shape.

On one face of a stationary insulating support 35 surrounding and closely adjacent to the rotor 30 are mounted terminal members 35 and 3'! adapted to have potentials impressed thereon and in sliding engagement respectively with the arcuate contact members 32 and 33, and two sets Q of terminal members 38 to 4| and 42 to 45 adapted to be connected to windings of transformers or the like corresponding to different frequency bands of a given stage and so arranged as to be engaged selectively by the extensions 45 and 41 of the arcuate contact members 32 and 33.

On the other face of the stationary insulating support 35 is mounted a fixed contact member 48, shown in Fig. 4, connected to ground and in constant sliding engagement with the. circular grounding member or plate 34. On this other face of the support 35 are also mounted two sets.

of terminal grounding members 49 to 52 and 53 to 56, preferably opposite to and connected respectively, as by clamping members such as 51 extending through thg support 35, to the terminals 38 to 4| and 42 t 45. The grounding members 49 to 52 and 53 to 56 are in sliding engagement with the rotatable grounded plate 34' except at recesses 58 and 59 formed iii the outer edge thereof, these recesses being in alignment respectively with the extensions 45 and 41 of the arcuate contact members 32 and 33.

In order to reduce the intensity of oscillations tending to be transmitted to the operating shaft from the switch elements upon which high frequency oscillations are impressed, and particularly from the arcuate contact members 32 and 33 which are of considerable length and which are located relatively close to the shaft, I have provided the shielding plate, 80, between these arcuate contact plates and the shaft opening 3|. The

shield plate 60 is so formed as substantially to cover the space on the face of insulating rotor 30 not occupied by the contact plates 32 and 33 and with small clearance between the shields outer edge and the inner edge of the latter contact shield plate 29 may be conveniently accomplished plates and between the shields inner edge and the shaft. v

The shield plate 60 is connected to the circular grounding plate,34 preferably by wire or rivet members ii to 53 traversing corresponding holes of a row of holes formed in rotor 30 near the outer edge thereof. Wire or rivet members are also provided connected to the shield plate 53 and traversing all other holes also of the row except those holes utilized in mounting the arcuate contact members 32 and 33 to the rotor. The latter contact members are connected to the rotor preferably by the oppositely, spaced pairs of rivets 34, 35 and 35, 31.

It has been found that the numerous conductive wireor rivet members, thus connected to the grounded shield plate 33 and filling a large proportion of the closely spaced holes formed in the edge of the rotor, function effectively as an added shielding means and aid materially in reducing the intensity of undesired -oscillations transmitted tothe shaft from the switch elements upon which, oscillations are impressed.

Referring to Figs. 5 and .6, the switch assembly illustrated therein may be in general essentially similar to that illustrated in Figs. 2 to 4. In the embodiment in Figs. 5 and 8, however,

- ment, said cont if 'a I therotor member, 88, is provided with an opening 69, which is of such form and size that it may be traversed by a metal shaft Ill, which is enclosed within a tubular shield member H and insulated therefrom by insulation material or an insulating member 12. The tubular shield is v grounded, preferably by connection, as by a.

member 13, to the circular grounding plate 14 which is itself grounded through the contact member 15.

The shaft 10, shieldedby a separate grounded tubular member at each switch assembly, may,

' apparatus such as multi-band radio receivers by the coupling through the gang-switch metal shaft have been materially reduced. For example, by adding, in such apparatus, a shielding member tact element of at least one of said switches and connected to the corresponding one of said grounding elements, said shield being insulated shield mounted between said shaft and the confrom both said shaft and said contact element.

- 3. A switch including a rotor of :insulating material, a shaft of conductive material traversing said rotor, a contact plate adapted to have oscillations impressed thereon and mounted on one side of said rotor, a grounding plate mounted on the'other side of said rotor, and a shield plate of conductive material mounted on said rotor between said contact plate and said shaft and connected tosaid grounding plate, said shield plate being insulated from both said shaft and u said contact plate.

. 4. In radio apparatus and the like including a plurality of switches, 'each of said switches having a contact supporting stator member and a movable insulating contact-supporting member,

""a' single operating shaft of conductiv material 60 as described in connection with Figs. 2 to 4 to the local oscillator switch assembly, I have effected a tenfold reduction in the undesired oscillator. radiation transmitted through the gang-switch shaft;

My invention has been described herein in particular embodiments for purposes of illustrations It will be understood, however, that the invention is susceptible of variouschanges and modiflcations and that by the appended claims I intend to cover any such modifications as fall within the true spirit and scope of my invention.

What'I claim as new and desire to secure by Letters Patent of'theUnited States is:

1. In radio apparatus and the like including a plurality of coaxially spaced switches having a single conductive shaft, for operation thereof, means to reduce'und'esired coupling effects between the circuits connected to said switches due to said shaft including means operatively associated with at least one of said switches to shield said shaft from ungrounded contact portions of said one switch, said shielding means being intraversing said movable members and tending t0 cause undesired coupling in said apparatus,.

means to reduce said coupling comprising a plurality of tubular shields, a respective one of said shields encircling said shaft at each of said switches and insulated from said shaft, and means to ground each of said shields.

5. In radio apparatus and the like including a plurality of coaxially spaced switches having a singl conductive shaft for operation thereof, each of said switchescomprising a stator member having a plurality of contacts carried thereby,

a rotor membercomprising an insulating disk apertured to accommodate said shaft, said rotor member having a pairof contacts for selectively engaging contacts on'said stator member, and means to reduce undesired coupling effects be- 1 tween the circuits connected to the contacts of different ones of said switches and due to said shaft, said means comprising a conductive shield mounted on the insulating disk 01' at least one of said switches between said pair of contacts and said shaft, and means to groundsaid shield.

sulated from both said ungrounded contact portions and said shaft, and means to ground said shielding means independently of said shaft.

2'. In radio apparatus and the like including at least two switches having contact supporting stator members and movableinsulating supporting members operated by; single shaftof conductive-material, each of said movable members having'a contact element and a grounding elenected to one of the contacts onsdid stator member by rotation of said shaft, said rotor members being coax'ially spaced on said shaft and said 6. In a radio apparatus, the combination of a plurality of coaxially spaced switches having a single conductiv shaft for operation thereof, each of said switches comprisingaa stator mem .ber having a plurality of contacts carried thereby, a rotor member comprising a flat insulating.

' disk apertured to accommodate said shaft, said act element being selectively conshaft tending undesirably to couple the circuits,

-connected to the contact elements on said switches, and means to. reduce undesired currents in said circuits due to the coupling effect of said shaft, said means comprising a conductive rotor member having mounted on one, face thereof a pair of contacts for selectively engaging contacts on said stator member, a flat grounding plate mounted on the opposite face of said disk and engaging the remain ng contactson said stator member, and means to reduce undesired coupling effects between the circuits connected 'to different ones of said switches and due to said shaft, said means comprising a conductive shield mounted on said one face of said switches between saidpair of contacts and said shaft, and means to ground said shield.

HARRY R AYER' 

